Power source thermal management and emissions reduction system

ABSTRACT

A power source may have at least one combustion chamber, a first valve configured to control an airflow between an air source and the at least one combustion chamber and a second valve configured to control an exhaust gas flow between the combustion chamber and an exhaust system. The power source may also have a fuel source configured to supply a fuel to the at least one combustion chamber and a controller operatively connected to the first valve and the second valve. The controller may be configured to determine one or more temperatures and, if the one or more temperatures are below a predetermined threshold, cause the first valve to substantially limit the airflow to the combustion chamber and cause the second valve to substantially limit the exhaust gas flow from the combustion chamber, such that a combustion stroke of one or more combustion cycles is executed with air substantially provided during an intake stroke of a previous combustion cycle.

TECHNICAL FIELD

This disclosure pertains generally to reduction of particulate and otheremissions from a power source and, more particularly, to the use ofvariable valve operation for thermal management and emission control.

BACKGROUND

Government standards associated with combustion engine emissions haveincreased the burden on manufacturers to reduce the amount ofparticulate and other emissions that may be exhausted from theirengines. For example, Environmental Protection Agency regulationsrequire a 90 percent reduction in emissions of oxides of nitrogen (NOx)and particulate matter (e.g., hydrocarbons and soot) for the year 2007.Manufacturers also have a commitment to their customers to producepowerful yet fuel efficient engines. However, the sometimes inverserelationship between fuel economy/power and reduced emissions tends tomake the task of reducing emissions while meeting customer needs adaunting one.

Exhaust after-treatment systems, including regenerative particulatefilters (RPFs) and selective catalytic reduction (SCR), provide methodsfor removing particulate and other emissions (e.g., NOx) from fossilfuel powered systems for engines, factories, and power plants. RPFs maycapture particulate matter within exhaust gas, composed primarily ofunburned hydrocarbons, and then oxidize the particulate matter, usingactive or passive regeneration cycles, into carbon dioxide and water,among other things. During typical SCR, a catalyst may facilitate areaction between exhaust gas NOx and a reductant, for example, ethanol,to produce nitrogen gas and byproduct substances such as water andnitrogen, thereby removing NOx from the exhaust gas. It is important tonote that while the term “exhaust gas” may indicate a substance that isprimarily gas phase, exhaust gas, as a byproduct of combustion, may alsocontain substances in solid or liquid phase. For example, particulatematter described herein may be included within exhaust gas and may be insolid or liquid phase. One of skill in the art will understand that theterm “exhaust gas” is intended to refer to all such substances generatedas a byproduct of combustion.

By capturing particulate matter, particulate filters may eventuallybecome clogged and unusable without a method for “regeneration.”Regeneration may be passive or active and is the process by which aparticulate filter may “remove” the collected particulate matter byoxidation (e.g., burning). A negligible amount of ash may remain in theparticulate filter following regeneration, and such accumulations may becleaned manually at desired intervals.

Active regeneration may involve the addition of heat, such as electricalresistance heat, to an RPF to facilitate oxidation of the particulatematter. Passive regeneration may facilitate oxidation of the particulatematter in the presence of a catalyst, without the addition of heat,provided the exhaust gas is maintained at a minimum oxidationtemperature (e.g., above about 200 degrees C.). When the exhaust gastemperature falls below the minimum oxidation temperature, the passiveRPF may be unable to successfully oxidize particulate matter and theflow of exhaust through the RPF may, therefore, be reduced or stoppeddue to the trapped particulate matter. Limited exhaust flow may, inturn, cause increased backpressure in the exhaust system. Such increasedbackpressure may then lead to significant performance degradation and apossible uncontrolled regeneration event within the RPF. Uncontrolledregeneration may further lead to a cracked or otherwise damaged RPFamong other things. For example, under cold start and/or low loadconditions (e.g., engine idle or near idle), exhaust gas temperaturesmay fall below the minimum oxidation temperature. The passivelyregenerated particulate filter may then begin to fill with particulatematter and the exhaust backpressure may increase. Oxidation of thetrapped particulate matter may then occur in an uncontrolled burnresulting in damage or destruction of the RPF. Because of this, manyengines utilizing passively regenerated particulate filters must besupplemented by an active regeneration or other similar system tofacilitate controlled regeneration at exhaust temperatures below theminimum oxidation temperature.

An SCR system typically includes injection and mixing of a reductant(e.g., ethanol) into the exhaust gas upstream of a catalyst tofacilitate a reaction in the presence of the catalyst. Operation of anSCR after-treatment system may also depend upon maintaining a minimumtemperature of both the catalyst and the exhaust gas, with highertemperatures generally improving the reaction between the reductant andNOx. While the performance of a lean-NOx catalyst to reduce NOx maydepend upon many factors, such as catalyst formulation, the size of thecatalyst, mixing of the reductant within the gas, the reductantcompound, and reductant dosing rate, it is important that the minimumtemperature be maintained such that the SCR continues to operateeffectively. Therefore, under cold start and low load conditions (e.g.,engine idle or near idle), where the exhaust-gas temperature falls belowa minimum reaction temperature, the efficiency of the SCRafter-treatment may be greatly reduced or the reaction halted resultingin increased NOx emissions.

Lean burn power sources may operate with an excess amount of air foreach power cycle and depending on operating conditions (e.g., load,temperature, etc.), the excess may be three to ten times the amount ofair necessary to combust fuel present in the combustion chamber. Thismay result in more complete combustion of the fuel and greater fuelefficiency. Once the fuel in the combustion chamber is burned, theexcess air (now heated from combustion), as well as any remaininghydrocarbons may be exhausted with the exhaust gas generated bycombustion to the exhaust system. While the lean mixture may result ingreater fuel efficiency, such a mixture may also lead to highercombustion temperatures and therefore greater NOx production. Some powersources may rely on methods such as exhaust gas recirculation, forexample, to lower combustion chamber temperatures and reduce NOxformation. But lower combustion chamber temperatures, particularly atlow load, may lead to lower exhaust-gas temperatures, which may in turndecrease or terminate the operation of exhaust after-treatment systems.

Some power sources may rely on combustion chamber deactivation to warmexhaust after-treatment systems at cold start, increase fuel economy,and reduce power source emissions output at low loads. The term“combustion chamber” may be used interchangeably with the term“cylinder” throughout this disclosure. It is to be understood that anengine cylinder may include a combustion chamber and, therefore,“cylinder” may also refer to a combustion chamber. Such power sourcesmay include mechanisms for disabling a group of cylinders within thepower source by stopping the flow of fuel to the targeted cylinders. Forexample, a six cylinder power source may include a variable valvemechanism to stop intake valve operation and fuel delivery for three ofthe six cylinders, effectively shutting off those three cylinders. Whilesuch a system may be useful for increasing fuel efficiency and reducingemissions output from the power source, the systems may be unable tomaintain a minimum exhaust temperature to facilitate operation of anexhaust after-treatment system at low loads or idle while alsoresponding quickly to increased demand for power.

One system using cylinder deactivation for limiting cold start emissionsis disclosed in U.S. Patent No. 6,931,839 to Foster (“the '839 patent”).The system of the '839 patent includes a mechanism for redirecting fuelflow, disabling spark, and preventing movement of intake and exhaustvalves such that a group of cylinders may be deactivated during a coldengine start. A portion of the fuel that would normally be burned in thedeactivated group of cylinders is re-directed to the remaining activecylinders thereby leading to an increase in torque to overcome the addedresistance of the deactivated cylinders. Further, combustion temperaturein the active cylinders is increased via the increase in fuel combusted,which in turn leads to higher exhaust gas temperatures and fasterwarming of the catalytic converter to operating temperature.

While the system of the '829 patent may result in some additional heatadded to the exhaust gas, it requires that a group of cylinders bedeactivated via disruption of fuel flow, thereby operating the powersource in a less than optimal state. Operation under such conditions maylead to balance issues and may render a power source less responsive topower demands, as the inactive cylinders must be reactivated upon heavyload demand. Further, deactivating a group of cylinders, while injectingadditional fuel into the remaining active cylinders may lead to a richmixture thereby reducing fuel economy and potentially increasinghydrocarbon emissions. Moreover, the additional temperature increasederived from the combustion of additional fuel in active cylinders maynot warm the exhaust gas and exhaust after-treatment systems as quicklyas if all cylinders were operating at an increased combustiontemperature.

The present disclosure is directed at overcoming one or more of theproblems or disadvantages in the prior art power systems.

SUMMARY OF THE DISCLOSURE

In one aspect, the present disclosure is directed to a power source. Thepower source may include at least one combustion chamber, a first valveconfigured to control an airflow between an air source and the at leastone combustion chamber, and a second valve configured to control anexhaust gas flow between the combustion chamber and an exhaust system.The power source may also include a fuel source configured to supply afuel to the at least one combustion chamber and a controller operativelyconnected to the first valve and the second valve. The controller may beconfigured to determine one or more temperatures and, if the one or moretemperatures are below a predetermined threshold, cause the first valveto substantially limit the airflow to the combustion chamber and causethe second valve to substantially limit the exhaust gas flow from thecombustion chamber, such that a combustion stroke of one or morecombustion cycles is executed with air substantially provided during anintake stroke of a previous combustion cycle.

In another aspect, the present disclosure is directed to a power source.The power source may include at least one combustion chamber, an intakepassage fluidly connected to the at least one combustion chamber, anintake valve disposed between the intake passage and the combustionchamber, and an airflow control element, independent of the intake valveand configured to, upon activation, substantially limit an airflow fromentering the combustion chamber. The power source may also include anexhaust passage fluidly connected to the at least one combustionchamber, an exhaust valve disposed between the exhaust gas passage andthe combustion chamber, an exhaust flow control element independent ofthe exhaust valve and configured to, upon activation, substantiallylimit an exhaust gas from exiting the combustion chamber, a fuel sourceconfigured to supply a fuel to the at least one combustion chamber, anda controller operatively connected to the airflow control element andthe exhaust flow control element. The controller may be configured todetermine one or more temperatures and, if the one or more temperaturesare below a predetermined threshold, activate both the exhaust flowcontrol element and the airflow control element, such that airflow issubstantially limited from entering the combustion chamber and exhaustgas is substantially limited from leaving the combustion chamber for atleast one subsequent combustion stroke.

In yet another aspect, the present disclosure is directed to a methodfor operating a power source. The method may include the steps ofproviding at least a first fuel charge and a first air charge to acombustion chamber of a power source, combusting the first fuel chargein the combustion chamber resulting in an exhaust gas, and determiningone or more temperatures. If the one or more temperatures are below apredetermined threshold, the method may further include the steps ofactivating an airflow control element configured to substantially limita second air charge from entering the combustion chamber, activating anexhaust flow control element configured to substantially limit theexhaust gas from exiting the combustion chamber, and combusting at leastone subsequent fuel charge within the combustion chamber prior todeactivating the airflow control element and the exhaust flow controlelement.

In yet another aspect, the present disclosure is directed to a machine.The machine may include a frame, a traction device, and a power sourceoperatively connected to the frame and the traction device. The powersource may include at least one combustion chamber, a first valveconfigured to control an airflow between an air source and the at leastone combustion chamber, a second valve configured to control an exhaustgas flow between the combustion chamber and an exhaust system, a fuelsource configured to supply a fuel to the at least one combustionchamber, and a controller operatively connected to the first valve andthe second valve. The controller may be configured to determine one ormore temperatures and, if the one or more temperatures are below apredetermined threshold, cause the first valve to substantially limitthe airflow to the combustion chamber, and cause the second valve tosubstantially limit the exhaust gas flow from the combustion chambersuch that a combustion stroke of one or more combustion cycles isexecuted with air substantially provided during an intake stroke of aprevious combustion cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a pictorial representation of an exemplary machinehaving multiple systems and components that may cooperate to accomplisha task;

FIG. 2 schematically illustrates a power source capable of implementingthe disclosed systems and methods for thermal management and emissionsreduction; and

FIG. 3 is a flowchart depicting one exemplary method for operation ofthe disclosed systems and methods.

DETAILED DESCRIPTION

FIG. 1 provides a pictorial representation of an exemplary machine 5having multiple systems and components that may cooperate to accomplisha task. Machine 5 may include a system for thermal management andemissions reduction. Machine 5 may embody a fixed or mobile machine thatperforms some type of operation associated with an industry such asmining, construction, farming, transportation, or any other industryknown in the art. For example, machine 5 may be an earth moving machinesuch as an excavator, a dozer, a loader, a backhoe, a motor grader, adump truck, or any other earth moving machine. In addition, machine 5may be an on- or off-road vehicle including, for example, heavy andlight trucks or an automobile. Machine 5 may include a power source 18and an input member 16 connecting a transmission assembly 10 to powersource 18 via a torque converter 19. Machine 5 may also include a frame14 and an output member 20 connecting the transmission assembly 10 toone or more traction devices 77 operatively connected to frame 14. Powersource 18 may be operatively connected to frame 14 and may further befluidly connected to an exhaust system 17, which may in turn be fluidlyconnected to an RPF 23 and/or an SCR system catalyst 31.

FIG. 2 schematically illustrates a power source capable of implementingthe disclosed systems and methods for thermal management and emissionsreduction. In an exemplary emissions reduction system, power source 18includes an internal combustion engine, e.g., a diesel engine, agasoline engine, a gaseous fuel-powered engine, and the like, or anyother lean-burn engine apparent to one skilled in the art. Power source18 may include, for example, an intake manifold 26, intake passages 24;exhaust passages 29, an exhaust manifold 28, combustion chambers 30,airflow control elements 25, exhaust flow control elements 27, and fuelsources 38. Power source 18 may further include a fuel pump 34, fuelstorage 36, and a controller 52.

Each of combustion chambers 30 may be configured with a slideablymounted piston (not shown) and may be configured to receive and combustmaterials including fuel and air, among other things (e.g., performanceenhancing substances). A piston associated with a combustion chamberfrom combustion chambers 30 may be connected to a crankshaft (not shown)such that a rotation of the crankshaft results in a correspondingreciprocating motion of the piston.

Power source 18 may be configured to operate using a two-stroke,four-stroke, or any other suitable combustion cycle. A “stroke” may bedefined as one-half rotation of the crankshaft wherein the piston movesfrom top-dead-center to bottom-dead center or vice versa. A standardcombustion cycle may be based on power source configuration and definedas one complete set of piston strokes resulting in combustion of a fuelwithin combustion chambers 30 and a derivation of heat/power from thecombustion. For example, a four-stroke combustion cycle may include anintake stroke during which, air is provided to the combustion chamber, acompression stroke during which, the air is compressed, a combustionstroke during which, fuel is combusted and power derived as the pistonis driven downward by the resulting expansion of gases, and an exhauststroke during which, the resulting gases are expelled from thecombustion chamber. Other suitable combustion cycles known in the artmay also be used without departing from the scope of this disclosure.

Combustion chambers 30 may be configured for compression ignition (CI),spark ignition (SI), homogeneous charge compression ignition (HCCI), orany other type of combustion ignition. For example, a diesel engine mayinitiate combustion as pistons (not shown) within combustion chambers 30near top-dead-center and critical temperature and pressure are reached.

Combustion chambers 30 may be configured to receive a supply of fuelfrom fuel sources 38. Fuel sources 38 may include injectors or atomizersconfigured to inject fuel directly into combustion chambers 30. Fuelsources 38 may be configured to supply fuel at a specific time (timedinjection) or, alternatively, may be configured to introduce fuelcontinuously or at random intervals. Configuration of fuel sources 38may depend upon the combustion configuration of combustion chambers 30(e.g., CI, SI, or HCCI and two-stroke, four-stroke, or other suitableconfiguration).

Fuel sources 38 may be operatively connected to fuel pump 34. Fuel pump34 may be configured to deliver fuel from fuel storage 36 to fuelsources 38. Fuel pump 34 may include an injection pump of the rotary ordistributor variety, or any other suitable pump, and may be drivenindirectly by gears or chains from the crankshaft or by other methods(e.g., electrically). One of skill in the art will recognize that manytypes of pumps may function adequately and fall within the scope of thecurrent disclosure.

The fuel supplied to combustion chambers 30 may include, for example,diesel fuel, gasoline, alcohols, propane, methane, or any other suitablefuel. The fuel may be supplied to fuel sources 38 under pressure, and/orfuel sources 38 may, themselves, be configured to further increase thepressure or velocity of the fuel. Fuel storage 36 may be configured tostore fuel, among other things, and may include a tank or other similarcontainer. Fuel may be supplied at timed intervals (e.g., based on powersource 18 rotational position), randomly, and/or continuously. Controlof the fuel source 38 may be regulated by methods known by those ofordinary skill in the art and appropriate for the type of power sourcein operation.

Intake manifold 26 may be configured to draw air from atmosphere or froman air source (e.g., a turbocharger) and provide an air charge tocombustion chambers 30 via intake passages 24. For example, intakemanifold 26 may be fluidly connected to a forced induction system suchas the outlet of a turbocharger or supercharger. Intake manifold 26 mayfurther be fluidly connected to at least one intake passage 24 which, inturn, may be fluidly connected to a combustion chamber 30. Fuel or otheradditive substances (e.g., performance boosting substances includingpropane) may also be supplied to intake manifold 26.

Intake passages 24 may be configured to carry substances including, air,fuel, and other substances, or any combination thereof, to combustionchambers 30. For example, at power source idle operation, intakepassages 24 may be configured to provide an air charge to combustionchambers 30 containing between about three and ten times the amount ofair necessary to execute one combustion stroke of a combustion cycle.

Intake passages 24 may be opened to combustion chambers 30 via intakevalve assemblies (not shown) and/or airflow control elements 25 whichmay open and close as desired to facilitate, substantially limit, orstop the flow of materials (e.g., air) into combustion chambers 30.Airflow control elements 25 may include valves, flaps, actuators, andother components suitable for enabling or limiting flow of a gas througha passage (e.g., intake passages 24). Airflow controls elements 25 mayfunction as and take the place of intake valve assemblies, oralternatively, both airflow control elements 25 and intake valveassemblies (not shown) may be present. Further, airflow control elements25 may operate independently of separate intake valve assemblies (wherepresent) or may operate in tandem to control airflow to combustionchambers 30. Additionally, it is important to note that airflow controlelements 25 may be located in any location suitable for substantiallylimiting or stopping the flow of air to combustion chambers 30. Forexample, airflow control elements 25 may be located within intakemanifold 26 or at an air source.

Airflow control elements 25 and intake valve assemblies associated withcombustion chambers 30 may be directly or indirectly connected to thecrankshaft by way of a timing device such that a rotation of thecrankshaft results in corresponding opening and closing movements of theassociated control or assembly. In addition, airflow control elements 25and intake valve assemblies may include mechanical and/orelectro-mechanical systems and may be activated or operated using anysuitable method (e.g., pushrod, solenoid, etc.) to allow, substantiallylimit, or stop the flow of air to combustion chambers 30. Further,airflow control elements 25 and intake valve assemblies maybeoperatively connected to controller 52 such that controller 52 mayaffect an activation or deactivation of both airflow control elements 25and intake valve assemblies. Intake passages 24 may contain more orfewer elements as desired.

Combustion of a first fuel charge within combustion chambers 30 mayresult in at least a portion of the fuel reacting with a portion of anair charge provided to combustion chambers 30 during an intake stroke.Heat and/or power may be derived from the combustion of the fuel and airand, as a result, an exhaust gas including particulate matter (e.g.,unburned hydrocarbons), NOx, CO₂, and water, among other things, may begenerated. Because the initial air charge may have contained three toten times the amount of air necessary for combustion, the exhaust gasmay be mixed with remaining air within combustion chambers 30. Dependingon current temperatures and operating conditions, the remaining airwithin combustion chambers 30 may allow subsequent combustion strokes tobe executed within combustion chambers 30 without the introduction ofadditional air and without allowing the generated exhaust gas to exitcombustion chambers 30.

Exhaust passages 29 may be fluidly connected to combustion chambers 30and configured to receive the exhaust gas generated as a result ofcombustion of the fuel within combustion chambers 30. The fluidconnection from combustion chambers 30 to exhaust passages 29 may beopened and closed via exhaust valve assemblies (not shown) and/orexhaust flow control elements 27 which may open and close as desired tofacilitate, substantially limit, or stop the flow of materials (e.g.,exhaust) out of combustion chambers 30. Exhaust flow control elements 27may include valves, flaps, actuators, and other components suitable forenabling or limiting flow of a gas through a passage (e.g., exhaustpassages 29). Exhaust flow control elements 27 may function as and takethe place of exhaust valve assemblies, or alternatively, both exhaustflow control elements 27 and exhaust valve assemblies (not shown) may bepresent. Further, exhaust flow control elements 27 may operateindependently of exhaust valve assemblies (where present) or may operatein tandem to control exhaust flow from combustion chambers 30.Additionally, it is important to note that exhaust flow control elements27 may be located in any location suitable for substantially limiting orstopping the flow of exhaust from combustion chambers 30. For example,exhaust flow control elements 27 may be located within exhaust manifold28 or within exhaust system 17.

Exhaust flow control elements 27 and exhaust valve assemblies associatedwith combustion chambers 30 may be directly or indirectly connected tothe crankshaft by way of a timing device such that a rotation of thecrankshaft results in corresponding opening and closing movements of theassociated control or assembly. In addition, exhaust flow controlelements 27 and exhaust valve assemblies may include mechanical and/orelectromechanical systems and may be activated or operated using anysuitable method (e.g., pushrod, solenoid, etc.) to allow, substantiallylimit, or stop the flow of an exhaust gas from combustion chambers 30.Further, exhaust flow control elements 27 and exhaust valve assembliesmay be operatively connected to controller 52 such that controller 52may affect an activation or deactivation of both exhaust flow controlelements 25 and exhaust valve assemblies.

Exhaust passages 29 may also be fluidly connected to an additive supplydevice 44 configured to provide an SCR reductant and/or an RPF catalystto the exhaust gas. For example, additive supply device may inject anSCR reductant (e.g., ethanol or urea), to exhaust gas flowing out ofcombustion chambers 30 such that upon reaching SCR system catalyst 31,NOx emissions may be reduced. Although additive supply device 44 isdepicted in FIG. 2 as being fluidly connected to exhaust system 17,additive supply device 44 may be located at any suitable location forproviding an additive to the exhaust gas. For example, additive supplydevice 44 may also be located at exhaust manifold 28, exhaust passages29, exhaust system 17, or any other suitable location for providing anadditive to the exhaust gas stream.

Exhaust manifold 28 may be fluidly linked to at least one exhaustpassage 29 and may collect and receive an exhaust gas from the at leastone exhaust passage 29. Exhaust manifold may operate to link severalexhaust passages 29 together and receive the cumulative exhaust fromexhaust passages 29. Exhaust manifold 28 may further include devices forsupplying other substances (e.g., urea, ethanol, etc.) for mixture inthe exhaust gas, or, alternatively, no such additional devices may bepresent. For example, exhaust manifold 28 may be fluidly connected toadditive supply device 44, which may be configured to supply an SCRreductant and/or an RPF catalyst additive to exhaust manifold 28.Exhaust manifold 28 may be well insulated to prevent heat loss andassist in maintaining exhaust temperatures conducive for operation of anRPF and/or an SCR system.

Exhaust manifold 28 may include sensors (not shown) for detectingexhaust-gas temperatures, levels of exhaust-gas pollutants, and levelsof other substances within the exhaust gas. Where the sensors indicatelow exhaust-gas temperatures, controller 52 may cause appropriate stepsto be taken to increase exhaust-gas temperatures (e.g., activatingairflow control elements 25 and exhaust flow control elements 27, amongother things). Exhaust manifold 28 may further include fluid connectionsto allow for recirculation of some exhaust gas and/or coupling ofexhaust gas to the turbine of a turbocharger (not shown), among otherthings.

Exhaust manifold 28 may be fluidly connected to an exhaust system 17,which may be configured to receive the exhaust gas from exhaust manifold28. Exhaust system 17 may include pipes, tubes, clamps, etc., and maydirect the flow of the exhaust gas in various directions. Exhaust system17 may also include sensors, mixing devices, and fluid connections torecirculation devices and turbocharger turbines (not shown), among otherthings.

RPF 23 may be fluidly connected to exhaust system 17 downstream ofexhaust manifold 28 and configured to receive an exhaust gas. RPF 23 maybe constructed from many materials and may be configured to removeparticulate matter from the exhaust gas using physical, chemical, orother suitable methods, and any combination thereof. For example, aparticulate filter utilizing physical methods of filtration may bemanufactured from semi-penetrable or semi-porous materials includingcoredierite and/or silicon carbide. The filter may include a honeycombtype structure and each channel within the structure may be blocked atalternating ends. Such a configuration may force exhaust gas flowinginto RPF 23 to pass through the semi-penetrable material into asurrounding channel. While exhaust gas may pass through thesemi-penetrable material, particulate matter within the exhaust gas maybe trapped on the walls of the semi-penetrable material, therebyremoving the matter from the exhaust gas. Other types of filters andmaterials may also be used including, for example, sintered metalplates, foamed metal structures, fiber mats, and any other suitablefiltration mediums.

RPF 23 may include a passively or actively regenerated particulatefilter, or may be a combination thereof. Regeneration of a particulatefilter may be useful for substantially limiting or eliminatingaccumulation of particulate matter within RPF 23. For example, apassively regenerated particulate filter may combust particulate matterwithin RPF 23 in the presence of a catalyst material and while exhausttemperatures are maintained above a predetermined temperature.Therefore, RPF 23 may include a metal promoter or catalyst dispersedwithin the filter material. The catalyst material may be designed tofacilitate combustion or oxidation of particulate matter within RPF 23such that substantial accumulation of particulates does not occur withinRPF 23. Such catalyst materials may include coatings of precious metals(e.g., platinum, silver, etc.) on the filter substrate. Additionally,injection of catalytic materials (e.g., heavy metals) into the exhaustgas stream, combustion chamber, or other suitable locations may also beused to aid in regeneration of RPF 23.

Passive RPF regeneration may oxidize particulate matter (e.g., carbonand hydrocarbon materials) and may proceed via multiple complex chemicalreactions. Simplified reactions may be summarized by the followingequations:

C+O₂→CO₂   (1)

NO₂+C→NO→+CO₂   (2)

NO+O₂→NOx   (3)

Carbon present in particulate matter may be combusted in the presence ofoxygen to produce CO₂ as shown in equation 1. By reacting in thepresence of a catalyst, the oxidation reaction may be initiated attemperature between about 200 degrees C. and 350 degrees C. As shown inequation 2, it may further be possible to react particulate matter withNO₂ to form NO and CO₂. The resulting NO may then react with availableO₂ to re-form NO₂ as illustrated by equation 3. While NO₂ is a NOxvariant, the resultant NO₂ may subsequently be treated utilizing SCRsystem catalyst 31 and a SCR reductant (e.g., ethanol) introduced to theexhaust gas stream, or by other suitable methods.

SCR system catalyst 31 may be disposed in exhaust system 17 downstreamof RPF 23, or, alternatively, may be disposed upstream of RPF 23 asdesired. Exhaust system 17 may direct flow of the exhaust gas such thatthe exhaust gas is received by SCR system catalyst 31 and caused tocontact the contained catalytic materials.

SCR system catalyst 31 may be made from a variety of materials. SCRsystem catalyst 31 may include a catalyst support material and a metalpromoter dispersed within the catalyst support material. The catalystsupport material may include at least one of alumina, zeolite,aluminophosphates, hexaluminates, aluminosilicates, zirconates,titanosilicates, and titanates. In one embodiment, the catalyst supportmaterial may include at least one of-alumina and zeolite, and the metalpromoter may include silver metal (Ag). Combinations of these materialsmay be used, and the catalyst material may be chosen based on the typeof fuel used, the ethanol additive used, the air to fuel-vapor ratiodesired, and/or for conformity with environmental standards. One ofordinary skill in the art will recognize that numerous other catalystcompositions may be used without departing from the scope of thisdisclosure. Further, multiple SCR system catalysts may also be includedin exhaust system 17.

The lean-NOx catalytic reaction is a complex process including manysteps. One of the reaction mechanisms, however, that may proceed in thepresence of SCR system catalyst 31 can be summarized by the followingreaction equations:

HC+O₂ oxygenated HC   (4)

NOx+oxygenated HC+O₂→N₂+CO₂+H₂O   (5)

SCR system catalyst 31 may catalyze the reduction of NOx to N₂ gas, asshown in equation (5). Further, as shown in equation (4), a hydrocarbonreducing agent may be converted to an activated, oxygenated hydrocarbonthat may interact with the NOx compounds to form organo-nitrogencontaining compounds. These materials may possibly decompose toisocyanate (NCO) or cyanide groups and eventually yield nitrogen gas(N₂) through the series of reactions as summarized above. A well mixedreductant (e.g., ethanol) within the exhaust gas may further react inthe presence of any remaining hydrocarbons (e.g., unburned fuel) inorder to aid in the production of oxygenated hydrocarbons, asrepresented by equation (4).

Controller 52 may be a mechanical or an electrical based controllerconfigured to control fuel flow, airflow, and exhaust flow, among otherthings, to and from combustion chambers 30. Controller may also beoperatively connected to intake and exhaust valves and/or airflowcontrol elements 25 and exhaust flow control elements 27. For example,controller 52 may send electric signals causing intake and exhaustvalves and/or airflow control elements 25 and exhaust flow controlelements 27 to open and close thereby allowing, substantially limiting,or stopping the flow of air and exhaust to and from combustion chambers30. Flow control may be based on factors including RPF temperature, SCRsystem catalyst temperature, exhaust-gas temperature, powerrequirements, emissions requirements, and other suitable parameters. Forexample, during low load or idle operation of power source 18, exhausttemperatures and/or RPF temperatures may fall below a predeterminedthreshold temperature for operation of RPF 23 and/or SCR system catalyst31 (e.g., around 200 degrees C.). Where a sensor present in RPF 23 orSCR system catalyst 31 indicates such a temperature condition,controller 52 may limit or stop the flow of air and exhaust byactivating airflow control elements 25 and exhaust flow control elements27, thereby effecting a decrease in current emissions to RPF 23 and/orSCR 31 and an increase in temperature of the resulting exhaust gas. Uponallowing the flow of exhaust and air, the increased temperature of theexhaust gas may allow RPF 23 and SCR system catalyst 31 to continueoperation.

Controller 52 may store data related to fuel to air ratios forcombustion in memory or other suitable storage location. Such data mayenable a determination of how many combustion cycles may be executedwithin combustion chambers 30 before deactivating airflow controlelements 25 and exhaust flow control elements 27 such that a fresh aircharge is allowed to enter and heated exhaust gas to exit combustionchambers 30. Data may be experimentally collected and based on enginesize, engine rotations per minute (RPM), engine load, among otherthings. Such data may be stored in a lookup table within controller 52for reference or data may be calculated using algorithms stored withincontroller 52 and based on similar parameters. For example, controller52 may contain data indicating that one combustion chamber of aparticular engine operating at 600 RPM may complete six combustionstrokes with a single air charge. Upon completion of six combustionstrokes, or upon other suitable conditions, controller 52 may cause afresh air charge to be introduced to combustion chambers 30 and exhaustgas to flow from combustion chambers 30.

INDUSTRIAL APPLICABILITY

The disclosed systems and methods may be applicable to any poweredsystem that includes an exhaust gas producing power source, such as anengine. The disclosed systems and methods may allow for thermalmanagement and emissions reduction from a power source. In particular,the disclosed systems and methods may assist in maintaining apredetermined exhaust-gas and catalyst temperature during idle andlow-load operation of the power source. Operation of the disclosedsystems and methods will now be explained.

Operation of combustion chambers 30 may be dependant on the ratio of airto fuel-vapor that is supplied during operation. When determining theair to fuel-vapor ratio, primary fuel as well as other combustiblematerials in combustion chamber 30 (e.g., propane, etc.) may be includedas fuel-vapor. The air to fuel-vapor ratio is often expressed as alambda value, which is derived from the stoichiometric air to fuel-vaporratio. The stoichiometric air to fuel-vapor ratio is the chemicallycorrect ratio for combustion to take place. A stoichiometric air tofuel-vapor ratio may be considered to be equivalent to a lambda value of1.0.

Combustion chambers may operate at non-stoichiometric air to fuel-vaporratios. A combustion chamber with a lower air to fuel-vapor ratio has alambda less than 1.0 and is said to be rich. A combustion chamber with ahigher air to fuel-vapor ratio has a lambda greater than 1.0 and is saidto be lean.

Lambda may affect combustion chamber and exhaust temperatures,emissions, and fuel efficiency. A lean-operating combustion chamber mayhave higher combustion temperatures, improved fuel efficiency, andresidual air within a combustion chamber following combustion ascompared to a combustion chamber operating under stoichiometric or richconditions. However, as lean operation may increase temperature, NOxproduction may also increase creating a need to maintain the temperatureof an SCR system catalyst at predetermined level for efficient NOxreduction.

During low load and idle of a power source, lambda values of between 3.0and 10.0 may be found within a combustion chamber following a firstintake stroke. Also during such operation, exhaust gas temperatures mayfall because a minimal amount of fuel may be combusted to maintain idleand low load operation. Because RPFs and SCR systems may provide maximumefficiency when maintained at a predetermined temperature, a method formanaging the thermal output and exhaust emissions of an engine may beuseful. In an exemplary embodiment of the present disclosure, uponsensing a low exhaust or catalyst temperature (e.g., RPF catalyst and/orSCR catalyst) a controller may take appropriate action to manage thermalcharacteristics of the power source to effect a temperature rise inexhaust gas while controlling power source emissions.

FIG. 3 is a flowchart depicting one exemplary method for operation ofthe disclosed systems and methods. FIG. 3 will be discussed in thecontext of a single combustion chamber 30, but it is to be understoodthat the operations described may apply to one or more combustionchambers 30. In one embodiment, during a first combustion cycle, an aircharge may be provided to combustion chamber 30 (step 300). The aircharge may be provided during an intake stroke of a piston mountedwithin combustion chamber 30. During low load and/or idle operation,lambda values may be in the range of 3.0 to 10.0. Following theprovision of an air charge, fuel may be provided to combustion chamber30, for example via fuel sources 38 (step 305). The fuel may then becombusted in combustion chamber 30 and power derived from the resultingexpansion of gases (step 310). Following combustion, controller 52 maymake a determination as to whether there is sufficient air remaining incombustion chamber 30 to execute another combustion stroke withincombustion chamber 30 (step 315). Such a determination may be based onengine load, the number of combustion strokes since the last fresh aircharge, and/or size of combustion chamber 30, among other things. Wherecontroller 52 determines there is sufficient air (step 315: yes),controller 52 may determine whether a temperature or multipletemperatures are below a predetermined threshold temperature (e.g., 200degrees C.) (step 320). For example, controller 52 may monitortemperatures of RPF 23 and SCR system catalyst 31. Where controller 52determines that the temperature or temperatures are below apredetermined threshold (step 320: yes), controller may determinewhether airflow control elements 25 and exhaust flow control elements 27are currently activated and substantially limiting or stopping the flowof air into combustion chamber 30 and exhaust out of combustion chamber30 (step 325). If airflow control elements 25 and exhaust flow controlelements 27 are currently activated (step 325: yes), fuel may once againbe provided to combustion chamber 30 (step 305) and the processrepeated. If airflow control elements 25 and exhaust flow controlelements 27 are not currently activated (step 325: no), controller 52may cause the airflow control elements 25 and exhaust flow controlelements 27 to be activated (step 330) which may result in a substantiallimitation or stoppage of the flow of air to combustion chamber 30 andexhaust gas from combustion chamber 30. Fuel may then be provided tocombustion chamber 30 (step 305).

Where controller 52 determines that insufficient air exists withincombustion chamber 30 (step 315: no) or that a temperature ortemperatures are above a predetermined threshold (step 320: no),controller 52 may cause the deactivation of airflow control elements 25and exhaust flow control elements 27 (step 335) allowing exhaust gas toflow from combustion chamber 30 into exhaust manifold 28 and a fresh aircharge to flow through intake passage 24 into combustion chamber 30. Afluid connection between exhaust manifold 28 and exhaust system 17 maythen allow the exhaust gas to be received by exhaust system 17. Exhaustsystem 17 may be configured to direct the exhaust gas flow through RPF23 and/or SCR system catalyst 31 via a fluid connection (step 340).Because the exhaust gas may be maintained at least above a minimumtemperature, RPF 23 may be enabled to filter and regenerate particulatematter, while SCR system catalyst 31 may reduce NOx emissions. This mayresult in the reduction efficiencies for particulate matter and NOxemissions greater than 90 percent and may meet federal regulations foryear 2007 emissions.

Several advantages may be associated with the disclosed systems andmethod for power source thermal management and emissions reduction. Forexample, because a power source may continue to operate all combustionchambers, the power source may maintain balance and may be moreresponsive to sudden demands for additional power. Maintenance of powersource balance may result in smoother low-load and idle operation. Also,there may be little or no lag time during re-activation of combustionchambers because the combustion chambers may continue to operate duringthermal management.

Moreover, by continuing to provide fuel to all combustion chambers ofthe power source, more efficient combustion may be achieved by limitingcombustion of rich mixtures within the combustion chambers. While lambdamay decrease as additional combustion strokes occur, lambda may not fallbelow a predetermined value before additional air is introduced. Thismay lead to more efficient lean combustion and therefore, to better fueleconomy and an overall reduction in hydrocarbon and other emissions.

Additionally, because combustion may continue in all cylinders, morefuel may be burned than if a portion of the cylinders were combustingadditional fuel. More fuel being combusted may then result in a greaterpotential temperature rise of the resulting exhaust gas. This may,therefore, allow an RPF and an SCR system to reach and maintain aminimum or optimal operating temperature during low-load or idleoperation in a decreased amount of time.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed system andmethods for power source thermal management and emissions reduction.Other embodiments will be apparent to those skilled in the art fromconsideration of the specification and practice of the disclosed systemsand methods for power source thermal management and emissions reduction.It is intended that the specification and examples be considered asexemplary only, with a true scope being indicated by the followingclaims and their equivalents.

1. A power source, comprising: at least one combustion chamber; a firstvalve configured to control an airflow between an air source and the atleast one combustion chamber; a second valve configured to control anexhaust gas flow between the combustion chamber and an exhaust system; afuel source configured to supply a fuel to the at least one combustionchamber; and a controller operatively connected to the first valve andthe second valve, wherein the controller is configured to: determine oneor more temperatures; and if the one or more temperatures are below apredetermined threshold, cause the first valve to substantially limitthe airflow to the combustion chamber and cause the second valve tosubstantially limit the exhaust gas flow from the combustion chamber,such that a combustion stroke of one or more combustion cycles isexecuted with air substantially provided during an intake stroke of aprevious combustion cycle.
 2. The power source of claim 1, furtherincluding a particulate filter fluidly connected to the exhaust gassystem.
 3. The power source of claim 2, wherein the one or moretemperatures include at least one of an exhaust gas temperature, aparticulate filter temperature, or a temperature associated with thepower source.
 4. The power source of claim 2, wherein the particulatefilter is configured for passive regeneration.
 5. The power source ofclaim 1, wherein the predetermined threshold is between about 200degrees C. and about 350 degrees C.
 6. The power source of claim 1,further including: a selective catalytic reduction system fluidlyconnected to the exhaust system.
 7. A power source, comprising: at leastone combustion chamber; an intake passage fluidly connected to the atleast one combustion chamber; an intake valve disposed between theintake passage and the combustion chamber; an airflow control element,independent of the intake valve and configured to, upon activation,substantially limit an airflow from entering the combustion chamber; anexhaust passage fluidly connected to the at least one combustionchamber; an exhaust valve disposed between the exhaust gas passage andthe combustion chamber; an exhaust flow control element independent ofthe exhaust valve and configured to, upon activation, substantiallylimit an exhaust gas from exiting the combustion chamber; a fuel sourceconfigured to supply a fuel to the at least one combustion chamber; anda controller operatively connected to the airflow control element andthe exhaust flow control element, wherein the controller is configuredto: determine one or more temperatures; and if the one or moretemperatures are below a predetermined threshold, activate both theexhaust flow control element and the airflow control element, such thatairflow is substantially limited from entering the combustion chamberand exhaust gas is substantially limited from leaving the combustionchamber for at least one subsequent combustion stroke.
 8. The powersource of claim 7, further including a particulate filter fluidlyconnected to the exhaust gas passage.
 9. The power source of claim 7,wherein the one or more temperatures include at least one of an exhaustgas temperature, a particulate filter temperature, or a temperatureassociated with a power source .
 10. The power source of claim 7,wherein the particulate filter is configured for passive regeneration.11. The power source of claim 10, wherein the predetermined threshold isbetween about 200 degrees C. and about 350 degrees C.
 12. The powersource of claim 7, further including: a selective catalytic reductionsystem fluidly connected to the exhaust passage.
 13. A method foroperating a power source, the method comprising: providing at least afirst fuel charge and a first air charge to a combustion chamber of apower source; combusting the first fuel charge in the combustion chamberresulting in an exhaust gas; determining one or more temperatures; andif the one or more temperatures are below a predetermined threshold:activating an airflow control element configured to substantially limita second air charge from entering the combustion chamber; activating anexhaust flow control element configured to substantially limit theexhaust gas from exiting the combustion chamber; and combusting at leastone subsequent fuel charge within the combustion chamber prior todeactivating the airflow control element and the exhaust flow controlelement.
 14. The method of claim 13, wherein the one or moretemperatures include at least one of an exhaust gas temperature, aparticulate filter temperature, or a temperature associated with thepower source.
 15. The method of claim 13, wherein the at least onesubsequent fuel charge is combusted such that the one or moretemperatures are maintained above about 200 degrees C.
 16. The method ofclaim 13, further including: de-activating the exhaust flow controlelement following the combustion of the at least one subsequent fuelcharge; causing the exhaust gas to be exposed to a regenerativeparticulate filter.
 17. The method of claim 16, wherein the regenerativeparticulate filter is configured for passive regeneration.
 18. Themethod of claim 17, further including: providing a particulate filterregenerative catalyst material to the exhaust gas.
 19. The method ofclaim 13, further including: providing a reductant substance to theexhaust gas; exposing the exhaust gas and the reductant to a selectivecatalytic reduction catalyst.
 20. The method of claim 13, furtherincluding: determining a remaining air charge within the combustionchamber; if the remaining air charge is below a predetermined limit,deactivating the airflow control element such that fresh air may beprovided to the combustion chamber.
 21. The method of claim 20, whereinthe determination is based on at least one of power source load,combustion chamber volume, power source rotational speed, orexperimental data.
 22. A machine, comprising: a frame; a tractiondevice; and a power source operatively connected to the frame and thetraction device, wherein the power source includes: at least onecombustion chamber; a first valve configured to control an airflowbetween an air source and the at least one combustion chamber; a secondvalve configured to control an exhaust gas flow between the combustionchamber and an exhaust system; a fuel source configured to supply a fuelto the at least one combustion chamber; and a controller operativelyconnected to the first valve and the second valve, wherein thecontroller is configured to: determine one or more temperatures; and ifthe one or more temperatures are below a predetermined threshold, causethe first valve to substantially limit the airflow to the combustionchamber, and cause the second valve to substantially limit the exhaustgas flow from the combustion chamber such that a combustion stroke ofone or more combustion cycles is executed with air substantiallyprovided during an intake stroke of a previous combustion cycle.